In the mid-2000s, before the smartphone revolution was fully cemented by iOS and Android, the mobile world was dominated by Java-enabled feature phones. Brands like Nokia (S40 series), Sony Ericsson, Samsung (non-OS models), and LG ruled the market. These devices ran on .
Nimbuzz was the king of J2ME VoIP. It supported Skype, GTalk, Yahoo, and MSN. The J2ME version allowed over Wi-Fi or GPRS, and voice calls via call-back (not pure VoIP). You can still find Nimbuzz .jar files on archive sites. Viber For Java J2me